[Traumatic Acid]

Hi all,
I've read about treatments for methanol poisoning and found that ethanol helps methanol bypass metabolism, thus preventing it from forming forming methanol acid and formaldehyde, sparing you serious harm. This makes sense to me, but it does raise the question; why would you bother denaturing ethanol with methanol? Seems like a waste of methanol to me. Typical methylated spirits is 95% ethanol and 5% methanol (apparently). According to wikipedia it takes about 10 ml of methanol to permanently damage the optic nerve. To ingest 10ml of methanol from methylated spirits one would have to consume 200 ml in a short period of time. At that point you will also have consumed 190 ml of pure ethanol which is far higher than a recreational dose and would probably render a lot of people unconscious anyway if consumed quickly.
Also this dose is far sufficient to treat methanol poisoning, a blood concentration of 100-150 mg/Dl is used to treat methanol poisoning and can be acheived with 48 ml of ethanol for a 70 kg person. Of course ethanol is not a 100% effective antidote, but the levels of methanol that would be ingested alongside a more appropriate dose of ethanol seem somewhat insignificant to me.
It doesn't add up to me. If anyone can explain to me why methanol is still used, and / or why I am wrong and explain how it is still harmful that would be great.

Also, just to clarify, I have no intention of drinking metho. In fact the methylated spirits you can buy in my area don't contain methanol, they contain various other undisclosed denaturants

Cheers.

[Corribus]

1, I suspect it is largely added as a deterrent. You don't want to add something that's going to immediately kill people, because desperate people have a tendency to drink denatured alcohol anyway. Somewhere along the line someone figured out that a bitterant was probably a better choice, because..

2, Acute effects are not the only effects. Optic nerve damage can be permanent and cumulative. Also, formic acid, and especially formaldehyde, both byproducts of methanol metabolism, can be carcinogenic or have other chronic effects.

[wildfyr]

Methanol will also make it taste very wrong

[Borek]

Methanol will also make it taste very wrong

From what I remember methanol doesn't taste much differently from ethanol. In most places what they sell as denatured alcohol is not contaminated with methanol, but with safer compounds which make it unpalatable (like some piridine derivatives, or denatonium).

[wildfyr]

I know reagent alcohol has ethyl acetate and a couple other small volatile molecules in it. You don't want complex nonvolatile molecules in reagent alcohol, it will complicate the reaction.

[Traumatic Acid]

1, I suspect it is largely added as a deterrent. You don't want to add something that's going to immediately kill people, because desperate people have a tendency to drink denatured alcohol anyway. Somewhere along the line someone figured out that a bitterant was probably a better choice, because..

2, Acute effects are not the only effects. Optic nerve damage can be permanent and cumulative. Also, formic acid, and especially formaldehyde, both byproducts of methanol metabolism, can be carcinogenic or have other chronic effects.

I see, so it would be the cumulative effects that do the damage. While the ethanol will not entirely rule out the effects of methanol it would mitigate them somewhat. Not something you'd want to rely on.

[Arkcon]

As was said, methanol is no longer used as a common denaturant for industrial purposes.  So on some level, this thread is just "cool trivia from years ago."

A small amount of methanol and isopropanol are added to denatured alcohol for laboratory disinfection.  Ethanol at 70% concentration is one of the best (but not absolutely the best: ref: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623738/) disinfectants around, and the methanol and isopropanol are good, but not as good as ethanol.  Thing is, they're chemically similar, so difficult to separate, and still useful for disinfecting applications, with negligible interference.

And that's the thing, maybe for some organic synthesis purposes, like an extraction, or chromatography, denatured with methanol alcohol still works fine.  I would want to use it to try and make diethyl ether.  Then again, I wouldn't be trying to make my own ethers anyway.

[Babcock_Hall]

There are now alternatives to using ethanol as an antidote.